A motor used as a drive source for a drainage pump of a washing machine, a washing pump of a dish washer, etc., is desired to have a highly reliable grounding structure because it is a product used near wet environments.
Conventionally, a so-called molded motor the stator of which is formed of a resin, is often used as a motor to be mounted on electric equipment intended for using water such as a washing machine, a dish washer, etc. In the case where the type of the molded motor is an induction motor with an inserter winding system, the grounding structure of the motor can be realized comparatively easily in a structure as described below. Namely, it is a structure in which a groove is provided on the outside diameter side of the stator core of the motor, so as to insert a grounding terminal in the groove, integrally mold them, and dispose the tip of the grounding terminal on the outside of the motor.
This conventional grounding structure is explained with reference to a drawing. FIG. 7 is a structural sectional view of a conventional molded motor.
In FIG. 7, on stator core 511, stator winding 512 is inserted in a slot (not shown) from the inside diameter side of stator core 511. Grounding terminal 514 is press fitted in the groove provided on the outside diameter side of stator core 511, and is molded by resin 531 forming the outer covering. The tip of grounding terminal 514 is exposed outside of resin 531 for connection with the grounding wire from the equipment side. Connector 513 is intended for connection with the wiring for power supply from the equipment to stator winding 512, and a part of this connector is fixed by molding with resin 531. Moreover, rotor 532, on which is mounted a shaft, is disposed on the inside of stator core 511. Bracket 533 mounting a bearing for supporting the shaft is fixed to the end face on one side of the stator.
Furthermore, another grounding structure is disclosed on Japanese Laid-Open Patent Application No. H11-75337. Namely, a method is known which consists of connecting the stator core and the bracket to the earth by means of a conductive elastic body, on a molded motor by mounting a conductive bracket by press fitting, on the end face in axial direction of a stator constructed by integrally molding the stator core and the stator winding wound around the stator core.
As still another grounding structure, a method is known which consists in connecting a pin, which is a rigid body, by pinching it between the stator core and the bracket.
However, in the case of a toroidal motor the stator winding of which is wound toward the outside diameter from a slot in the stator core, in particular, it is difficult to make the terminal come out from the outside diameter side of the stator core, because the stator winding is also wound on the outside diameter side of the stator core.
Still more, with only pinching of an elastic body, such as spring, etc., or a pin, which is a rigid body between the stator core and the bracket, the pinched part is in a state of point contact between the two, and the accuracy of the contact is low. For this reason, there is a risk of the contact becoming unstable because of secular change, etc., and therefore, its reliability as a grounding structure is rather low.